Hyperthermal beams sputtered from alkalihalide surfaces

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Abstract
Velocity selected beams of atoms and molecules have been produced by sputtering from various alkalihalide surfaces under 6 keV Ar+ ion bombardment. The mass spectrum and the velocity distribution of these particles have been analysed in the range from 0-1 3000 m/s. In the low velocity part of the spectrum monatomic particles as well as polyatornic ones have been found. For velocities larger than 3000 m/s the number of sputtered molecules is very small compared to the number of atoms. In addition to typical sputtering velocity distributions, thermal distributions are also found, due to vaporization of the less effectively sputtered atoms from the crystals. Above a few eV the energy distribution of a given alkali or halogen atom is independent of the target from which it is sputtered. There are indications that some sputtered atoms and molecules are formed in long lived excited states.